I have written and delivered a five-week programme aimed at reducing children's anxiety levels.
I tested participants' anxiety before and after the course using the Spence Anxiety Test. Spence standardises the raw data to typical children (t-scores, by age and gender).
I have also tested a 'random' group of similarly aged children from a general population. These kids have similar ages / gender mix, but have not been specifically selected for an anxiety course. Their mean anxiety t-scores are 50 (i.e. typical for their age/gender). The mean t-scores for the kids chosen for the course was 63 at the start of the course, indicating slightly elevated anxiety.
There were slight reductions in the average t-scores for both groups.
So far, I have data for 20 kids who have done the course and 20 'control' kids who did not do the course. I have their anxiety levels at week 1 and week 5 for both control group and subjects.
1/ How do I test whether my programme has made a difference (statistically)? Is there a statistical difference between the change in anxiety in the two group?)
2/ How many sample points should I am for?
I'm not a statistician (as you can probably tell), but I do have some (rusty) knowledge of stats. I'm pretty nifty with Excel, which I will use for data analysis.
Any help greatly appreciated! Thank you.